felixh@headcrash.Berkeley.EDU (Felix Hack) (11/29/90)
The Harpoon computer game's sonar model may be compared to the boardgame and to reality. Clearly we want it to be realistic, but the programmers are probably only interested in emulating the boardgame and hoping that system takes care of reality. While the computer game has the detection probabilities from the board- game built in, it's not possible to check whether all the sonar modifiers are done the same way (i.e. correctly). There's not even a uniform set of mods; take a look at the Harpoon ASW Forms Module for revisions to the sonar modifiers (higher speed to cavitate, for one thing). Regarding changing depth to break track, changing depth shouldn't work against CZ detections. The scale of CZ is concentric circles of width of order 5 miles at ranges of order 30 miles and multiples thereof. The diagrams are grossly off true scale since they show depths of 1000 feet as large as something like 5 miles horizontally. The RSR model seems reasonable. I have no access to data on real sonar performance vs hostile subs, but then who does? If you're trying to track enemy subs and you fail to detect them, you don't know it. Anyway, from all I've read and from playing lots of RSR I can't complain. In the computer game the LA creeps at 5 knots, the improved LA at 10. While the former speed earns a quieting and sonar improvement bonus, the improved LA's speed does not earn a creep bonus in the boardgame. The improved LA is merely quieter and gets a -10% detection mod. The same seems to hold for the Trafalgar; it too creeps at 10 knots on the computer and gets -10% for its shrouded propulsor. An LA at 0 knots still makes noise, since it has to operate machinery to keep the reactor cooled. This isn't much though. I've read that the boat is not any noisier cruising at a few knots than at full stop. I guess flow noise is low at first, and of course there's no cavitation at slow speeds. I've heard rumors that the boardgame's ASW will be revised. I sure hope the computer game follows suit. Felix
xrtnt@amarna.gsfc.nasa.gov (Nigel Tzeng) (11/30/90)
In article <1990Nov29.085633.20243@agate.berkeley.edu>, felixh@headcrash.Berkeley.EDU (Felix Hack) writes... ^ ^ The Harpoon computer game's sonar model may be compared to the boardgame ^and to reality. Clearly we want it to be realistic, but the programmers ^are probably only interested in emulating the boardgame and hoping that ^system takes care of reality. Understandable. One assumes that Larry Bond knows what he is doing and for the most part I would tend to say he does ;-). Much more than I anyway. ;-) ^ While the computer game has the detection probabilities from the board- ^game built in, it's not possible to check whether all the sonar modifiers ^are done the same way (i.e. correctly). There's not even a uniform set ^of mods; take a look at the Harpoon ASW Forms Module for revisions to ^the sonar modifiers (higher speed to cavitate, for one thing). ^ Regarding changing depth to break track, changing depth shouldn't work ^against CZ detections. The scale of CZ is concentric circles of width of ^order 5 miles at ranges of order 30 miles and multiples thereof. The ^diagrams are grossly off true scale since they show depths of 1000 feet ^as large as something like 5 miles horizontally. I thought it might be so. The objective isn't to break the contact but to wreck the target solution. The standoff torps have limited detection and range once in the water so it might land far enough away not to find me. Twas not to be. I also noticed that the MK48 never seems to go into active mode (in regard to speed). At 40 knots it isn't going to catch anything in a stern chase. It does manage though but the display (when I select it as the active group) seems to read that it is cruising all the way to impact. I noticed once that on the recieving end I had some ship moving at flank speed away from a torp (say a couple miles away) which was hit maybe 30 sec later. I had figured the torp beaten since the difference in speed was very low and the range reasonable large. At best it shouldn't have hit until quite a few minutes later. ^ The RSR model seems reasonable. I have no access to data on real sonar ^performance vs hostile subs, but then who does? If you're trying to track ^enemy subs and you fail to detect them, you don't know it. Anyway, from ^all I've read and from playing lots of RSR I can't complain. ^ In the computer game the LA creeps at 5 knots, the improved LA at 10. ^While the former speed earns a quieting and sonar improvement bonus, the ^improved LA's speed does not earn a creep bonus in the boardgame. The ^improved LA is merely quieter and gets a -10% detection mod. The same ^seems to hold for the Trafalgar; it too creeps at 10 knots on the ^computer and gets -10% for its shrouded propulsor. Does the game (I didn't look at the data files in that detail) actually know about the mods between ships within the classes? I recall noticing that the ROF for the Tico was low enough not to look like the VLS launches. If I recall correctly (and that's an iffy proposition at best ;-) the Trafalgar has the 7 blade prop and not the propulsor. Would you infer that it wouldn't get the 10% bonus? ^ An LA at 0 knots still makes noise, since it has to operate machinery ^to keep the reactor cooled. This isn't much though. I've read that ^the boat is not any noisier cruising at a few knots than at full stop. ^I guess flow noise is low at first, and of course there's no cavitation ^at slow speeds. Hmmm..I understand that it will make noise. The question is whether this value is much above ambient. If it isn't you'll need some real awesome signal processing gear to filter out noise from signal at that level. There was a decent article in the Proceedings a few years back about the diminshing returns on passive sonar technology as noise levels go below ambient. Detection ranges in that case is not dependent on how sensitive your instrument but how good your computer is at filtering out background. Either way the range goes way down and they were concerned that in that event the solitary US sub will face multiple quiet Soviet subs at close range. It may tag the first guy only to be sunk by the companions. We certainly can't trade one for one. I've gone to 19 knots as in general they detect me at 5 knots anyway. It minimizes the time to when I can shoot back and I can still hear him. This is kind of silly but in the game it works a bit better than creeping...at least against subs with standoff weapons. About the only time I win those encounters is to pick him up and send a Nimrod after him but I consider that cheating on my part ;-). ^ I've heard rumors that the boardgame's ASW will be revised. I sure ^hope the computer game follows suit. This'll be good...I know quite a few avid board gamers but we've never been able to get into Harpoon. The computer version is fairly popular among the crowd though. ^ ^ Felix NT -------------------------------------------------------------------------------- // | Nigel Tzeng - STX Inc - NASA/GSFC COBE Project \X/ | xrtnt@amarna.gsfc.nasa.gov | Amiga | Standard Disclaimer Applies: The opinions expressed are my own.
felixh@lightning.Berkeley.EDU (Felix Hack) (11/30/90)
The question of whether standoff torpedoes with non-nuclear warheads are really useful is not, to my mind, settled. It just seems very difficult to track an enemy sub so precisely at 30 miles as to drop a homing torp with a detection range of only 500 yards (for Mk46, maybe double for Mk50) directly on top. Note that the US SeaLance carrying Mk 50 was cancelled; I don't believe SSN16's torpedo is so great either. I think real torpedoes almost always accelerate to full speed by final approach to their targets. The extra noise doesn't matter because ASW torps are all active homers anyway. The Harpoon boardgame doesn't treat this accurately to save on record-keeping and keep things simple (but in Naval warfare I don't like simple). The computer game follows suit and seems to use the same system: Dual speed torps have two ranges and two speeds. If you fire outside the smaller range the torp runs at the slower speed all the way. If you fire inside the smaller range it goes high speed all the way. The on-line torpedo data doesn't show this, but the database reflects this and I've seen it while playing. This sets up some absurd situations. There are some really slow torps in the game, which if fired at long range can be easily outrun. For exampl,e if the fearsome Type 65 is fired outside 27 miles it goes at 30 knots. Just turn around and run away. Even at 20 knots it only catches up 10 miles per hour. Another bad one is if you fire just inside the 'fast' range, you don't get the choice to shoot slow (like you can in the boardgame) so you'll be sure of catching a relatively slow target. Sure, the torp is fast, but with only a little running the target is out of range. The game does not distinguish between ships of the same class; all Trafalgar class subs get a 10% quieting bonus, even though the lead ship (Trafalgar) doesn't have the shrouded propulsor. Missile launch rates from Aegis cruisers seem low in the game, but they're a bit off in the boardgame too. Has anyone seen the SAM-turnaround maneuver? This is a pretty bad programming choice in which SAMs that are roughly as fast as their targets fired not directly head-on will fly a pure pursuit path, often reversing course 180 deg to fly generally TOWARDS the ship that launched the SAM! If the SAM isn't faster it fails to catch its target altogether and thus automatically misses. So much for massed SM2 volleys knocking down AS-6 going for the carrier . . . . I've read that guided missiles use some more intelligent schemes to fly lead-intercept courses. That's how it's done in SimCan's Grey Seas Grey Skies, and you don't get flaky SAM flight. Felix